CN104120358A - Super-low-carbon steel containing trace tin element and having high strength, corrosion resistance and easy molding and preparation method thereof - Google Patents

Abstract

The invention discloses super-low-carbon steel containing a trace tin element and having high strength, corrosion resistance and easy molding. The super-low-carbon steel comprises the chemical composition by the mass percentage: 0.001-0.005% of C, 0.001-0.003% of N, 0.1-0.5% of Mn, 0.8-1.50% of Cr, 0.01-0.1% of Mo, 0.1-0.5% of Si, 0.005-0.01% of Al, 0.0001-0.0015% of Mg, 0.0001-0.0015% of Ca, 0.01-0.30% of Sn, 0.01-0.2% of Nb, 0.05-0.3% of Cu, 0.01-0.2% of Ti, 0.001-0.010% of P, not more than 0.003% of S, and the balance Fe. The steel material is prepared by smelting in an induction heating vacuum furnace, ingot casting, hot rolling, pickling and cold rolling, crystallization and annealing, and rolling, wherein the steel material contains trace tin, is low in carbon content and high in strength, has excellent complex workpiece forming performance and resistance to corrosion of oilfield produced water and other aqueous solution, and can be safely used in oil and gas field complex drilling and well completion and other environments; and the method is reliable in principle, simple in production process, convenient to operate, and high in practicality.

Description

A kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation and preparation method thereof

Technical field

The invention belongs to metal material field, relate to that having of need to working in modern industry field is corrosion-resistant in aqueous medium, high strength, high-mouldability can steel and preparation method thereof, particularly in industrial gas oil, relate to complex drilling with expansion pipe and high-level stage branch well bifurcation device etc. need anticorrosive, high strength, high-mouldability can steel and preparation method thereof for workpiece.

Background technology

IF (Interstitial-Free) steel claims again gapless atomic steel, and third generation deep drawing steel is to produce after the eighties in last century.The feature of IF steel is: carbon content is very low, after adding Ti and Nb, forms C, the N compound of Ti and Nb.Due to gap-free atom in steel, and make it have excellent deep drawability, high-ductility strain ratio, high-elongation, high hardenability value and lower yield tensile ratio, and there is the non-ageing of excellence.Traditional IF hardness of steel is very low, its yield strength R _ponly, less than 150MPa, to the higher workpiece of some requirement of strength, be difficult to applicable.In recent years in research, find, in IF steel, add the elements such as a small amount of Mn, Si and trace P (0.001～0.008%), B (0.001～0.008%) and can improve the intensity of IF steel, and then developed high-intensity IF steel, more than the yield strength of this high-intensity IF steel can reach 200MPa, keep good processability simultaneously, be referred to as high strength type IF steel.

But, for IF steel and the high-intensity IF steel that contains P, Mn, Si and micro alloying element, also the normal existence due to second phase particles causes the IF steel corrosion resistance that serious corrosion phenomena and grain growth cause to decline with the surperficial skewness because of Mn element.Therefore, for the workpiece that needs high-mouldability energy in industrial gas oil, as: in the complex drilling process in oil and gas industry for solving leakage and the hole diameter bulged tube technology steel pipes such as the large rate of expansion of employing (rate of expansion is greater than 20%) of narrow pressure density window, the six-stage branch well bifurcation that pressure-bearing is no more than 10MPa steel (bifurcated pipe that high-grade six-grade branch well is used for device, that an angle only has the large bevel tee of 1-3 °), due to these workpiece in use long period of soaking in the water base corrosive environment of high salinity of oil field mining liquid, the workpiece that adopts high-strength IF steel to make through complicated moulding, its anti-Corrosion Protection obviously can not meet the demand of Practical Project.Therefore for needing in industrial gas oil, be badly in need of developing high-mouldability can the good high-mouldability energy steel of high strength, corrosion resistance used of complex part.

Improve the resistance to corrosion of steel in aqueous medium, in steel, adding Cr element is the most effective means.Cr can form continuous solid solution with iron, dwindles the element of austenite phase region, and Cr forms fine and close, stable Cr in oxygenated environment ₂o ₃protective film; to stop medium to infiltrate to the continuation of metallic matrix the element that corrosion has very strong passivation ability; Cr adds the corrosion potential that can improve steel in steel to as alloying element in addition; reduce corrosion current; and reach finite concentration at Cr content; when the atomic ratio of Cr reach 1/8,2/8,3/8 ... n/8, the electropotential of iron-based sosoloid can increase great-jump-forward, and therefore corrosion also weakens.The corrosion resistance nature of steel can improve significantly, Cr is to one of weak element of the solution strengthening effect of steel, and at Cr content, be less than under 1.5% condition, along with the increase of steel Cr content, the corrosion potential of steel in group water solution increases, corrosion current reduces.According to the alloying principle of steel, when in steel, Cr content is high, to steel corrosion-resistant, can not improve more effective with adding combining of Cu element.Therefore in steel, combine interpolation Cr and Cu element the most effective for the corrosive power of the anti-aqueous medium of raising steel.

Sn element is periodic system of elements IVA family element, ordination number 50, nucleidic mass 118.69.Sn element is typical internal adsorption element in steel, very small with the amount of Fe formation sosoloid in steel, most of Sn element is at grain boundaries with low melting point metal form segregation, cause the high temperature hot workability containing Sn steel to degenerate, this just traditional metallurgical idea think that Sn element is the basic cause of harmful element in steel always.But also someone thinks, if do not consider the impact of Sn on steel high-temperature behavior, in steel, add pettiness amount Sn can improve the erosion resistance of steel, its intensity also improves, and plasticity is affected not quite.As: in cast iron, add micro-Sn element, the performance of raising cast iron that can be obvious.

In recent years, due to the development of smelting iron and steel technology, vacuum degassing technology RH, the VOD that particularly Clean Steel ultra-clean steel technology is followed, the development of AOD, the generation of the Ultra-low carbon super-purity ferrite stainless steel causing, and segregation highly malleablized is theoretical altogether ^[5]development, particularly 2010, Zhu Jin stainless steel company of Nippon Steel (NSSC) has established by adding the Sn element of mass ratio approximately 0.1%, the stainless Cr content of ferrite type (chromium class) can be reduced more than 3%, and the corrosion resistance nature of steel obtains the technology of tremendous raising simultaneously.The pioneering technology being with historically new significance in this whole world is that new approach has been opened up in the application in steel of the Sn element of thick atom size.

Due to the forming process of high-mouldability energy steel part, almost all through pull and stretch or punching press, carry out.Therefore, the processability of steel (being that steel plate is resisted inefficacy in bearing deformation process, as fracture, bent, wrinkling, the shape distortion of wooden dipper etc.) depends on characteristic and the texturizing condition of steel itself.The steel self performance here mainly refers to yield strength (Rp), the tensile strength Rm of the steel that obtain by one way tensile test), the percentage of total elongation (basic index of (A) and two important evaluation steel plate forming performances: i.e. Lankford r value and strain-hardening index n value.

For high formability energy steel, one in fact, should have lower yield strength, lower yield tensile ratio and higher unit elongation, and higher strain-hardening index n value and higher Lankford r value (r value is also referred to as the coefficient of normal anisortopy).

For strain-hardening index n: the true stress-true stain relational expression that is the distortion of Hollomon plastic elongation

σ＝Kε ⁿ (1)

Index n in formula, is called as strain-hardening index.

The physical significance of n value is the material parameter of the ability of exosyndrome material and steel pipe homogeneous deformation.N value is weave construction susceptibility parameter, and n is big or small, the Molecular segregation Chengdu of tissue is relevant with the stacking fault energy of material; N value is that in plastic history, evenly ability is a kind of measures for steel plate.For thin plate steel, its true homogeneous strain, is can have close ties with the stretching property of thin plate, and n value is higher, and stretching property can be better.

Because the sample actual measurement n value of cold-rolled steel sheet different orientation is different, so in Practical Project, be in steel plate plane, to get the tension specimen that becomes 0 °, 45 °, 90 ° with rolling direction, mean strain hardenability value n value formula is as follows:

$\stackrel{\‾}{n}=(n_0+{2n}_{45}+n_{90})/4---\left(2\right)$

For ultralow-carbon IF steel, the size of n value depends primarily on purity and the ferrite grain size of steel, improves the purity of steel and suitably reduce ferrite grain size to increase n value.After the n value and the relation between ferrite grain size of Morrison research mild steel plate, summarize following formula:

$n=5/(10+d^{-\frac{1}{2}})---\left(3\right)$

In formula, d is average crystal grain diameter, and unit is μ m.

The coefficient of normal anisortopy r value is true strain and the thickness direction true strain ratio of width in unilateral stretching sample drawing process,

r＝ε _w/ε _t (4)

This index is proposed in nineteen fifty by Lankford, and it is that a kind of of thin plate plastic anisotropy measures.Identical with work hardening exponent, the sample r value of different orientation is different, therefore define average plastic strain ratio or: r _mvalue and in-plane anisotropy value △ r are:

$\stackrel{\‾}{r}=(r_0+{2r}_{45}+r_{90})/4---\left(5\right)$

$\mathrm{\Δr}=(r_0-{2r}_{45}+r_{90})/2---\left(6\right)$

By (4), can be found out, r value is larger, and sheet material draws in swollen forming process the thin ability of resistance stronger, and deep drawability is better; R value is less, and material easily attenuation on thickness direction when distortion, easily causes cracking phenomena, and punching performance is bad.

(6) the △ r in formula has reflected the degree of uniformity of all directions r value on plate face, it and when stamping the size of lug there is close relationship, more lug is larger for △ r value.For making sheet deformation evenly reduce lug, △ r should be as far as possible little, when △ r=0, do not occur ears or side handles of a utensil defect.

Studies have shown that value depends on the preferable grain orientation (being texture) in steel plate, 111} texture is stronger, 100} texture more a little less than, higher, deep drawability is better.

Existing research is verified, and the texture of IF steel mainly forms in cold-rolled process, for the later stage can access more satisfactory annealing recrystallization texture, requires at the deformation texture of cold deformation stage formation enough strong.In cold-rolled process, intracrystalline dislocation starts slippage under external force, and in this process, its slip plane is tending towards rolling face gradually, slip direction be tending towards being parallel to roll to.Meanwhile, along with the continuous slippage of dislocation in crystal, also can there is corresponding rotation in the orientation of crystal.Along with the increase of cold-rolling of steel plate draft, each crystal grain in polycrystal can rotate gradually near a certain or some feature orientation, and then occurs the preferred orientation of crystal grain.And the degree of preferred orientation is along with the increasing of deflection strengthens.In cold deformation process, the grain orientation in IF steel is assembled on α orientation line and γ orientation line, and along with the increase of deflection, accumulated amount also increases thereupon.And research finds, in the cold rolling texture of IF steel develops, draught is 0～50% time, and gamma fiber texture has obvious growth, but when draught continues to increase, and the Strength Changes of gamma fiber texture is not with regard to not obvious; And the intensity of alpha fibers texture is along with the increase of draught has obvious growth all the time.So mainly comprising 4 kinds of texture components in cold rolling IF steel plate later, be respectively { 111}<110>, { 111}<112>, { 112}<110> and { 001}<110>.

Desirable texture in IF steel, is finally to form by the recrystallization annealing after heavy reduction cold rolling, and the nucleation and growth process of recrystal grain will occur the crystal grain being out of shape in annealing process, the formation of simultaneous annealing recrystallization texture.Here be mainly to be undertaken by " oriented nucleation " and " selecting growth " machine-processed theory, in steel plate, the nucleation and growth of different orientation crystal grain is a process of vying each other.So-called " oriented nucleation " refers to that the content of the IF steel gamma fiber texture component after recrystallization annealing after cold rolling is more, this is because the initial period in annealing has formed more γ orientation nucleus, and its speed of growth is very fast, i.e. " oriented nucleation " theory of recrystallize starting stage; In annealing process, the energy storage when motivating force of crystal grain recrystallize is cold roller and deformed, and between the size of this energy storage and grain orientation, exist certain relation.The cold rolling main four kinds of texture components later of IF steel, its size order that stores energy is E _{{ 111}<112>}>E _{{ 111}<110>}>E _{{ 112}<110>}>E _{{ 0 01}<110>}, therefore, in recrystallization annealing process, { 111}<112> stores can be the highest, and preferential forming core, is secondly { 111}<110>.And, { what form in 111}<112> deformation matrix is new { 111}<110> crystal grain, { what form in 111}<110> deformation matrix is new { 111}<112> crystal grain, and annex the crystal grain of other orientation in process of growth thereafter.And in the later stage of recrystallization annealing process, " selecting growth " that deformation stored energy causes plays keying action, after gross distortion, the nucleus of a large amount of different orientations is present in metallic matrix, only has those nucleus that correspond to the favourable orientation of modulated structure just can grow up during annealing.In IF steel recrystallization annealing nucleus growth process, { crystal grain of 111}<112> orientation is with { growing up of the crystal grain of 111}<110> orientation is exactly the result of this selection growth.As in the recrystallization annealing of IF steel after cold deformation why, can be formed with and benefit the γ desirable texture that deep drawability improves, studies have shown that it is that deleterious effect due to trace alloying element Ti that Ultra-low carbon and strong carbide form, Mn-C dipole that Nb causes alleviates with grain refining and causes.

In view of above technical background, contriver is on the basis of high strength third generation deep drawing steel IF steel, the micro alloying elements such as employing sublimate smelting technology, the Sn element that adds a small amount of raising corrosion resistance alloying elements cr, Cu, Mo and trace and Ti have been developed a kind of high-strength corrosion-resistant high-mouldability energy steel that contains micro-Sn element, and it is of value to sheet material processing and the tubing processing that improves processability, and be applied to, in the preparation of complicated equipment part in natural petroleum gas field, obtain good effect.

Summary of the invention

The object of the invention is to overcome the shortcoming of prior art, a kind of steel are provided, these steel are low containing trace tin, carbon content, intensity is high, there is the aqueous corrosion performances such as good complex part processability and anti-oil field extracted water, can in the complex drilling completion of oil-gas field and other environment, use safely.

Another object of the present invention is to provide this to contain the preparation method of the ultra low-carbon steel of trace tin element, high strength, corrosion-resistant and easy-formation, the method principle is reliable, and production technique is simple, easy and simple to handle, practical.

Object of the present invention is achieved through the following technical solutions:

The present invention is on the basis of high-strength IF steel, by Composition Design, vacuum metling, control, cast, cogging forging, hot rolling, to be greater than 80% draught cold rolling, and the process program of recrystallization annealing obtains a kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation of the present invention, can in containing water base corrosive medium environment, oil and gas field etc. apply.

A kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation of the present invention, it is composed as follows, is mass percent:

C:0.001～0.005%, N:0.001～0.003%, Mn:0.1～0.5%, Cr:0.8～1.50%, Mo:0.01～0.1, SI:0.1～0.5%, Al:0.005～0.01%, Mg:0.0001～0.0015%, Ca:0.0001～0.0015%, Sn:0.01～0.30%, Nb:0.01～0.2%, Cu:0.05～0.3%, Ti:0.01～0.2%, P:0.001～0.010%, S≤0.003%, all the other are Fe.

The preparation method of the above-mentioned ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation, it comprises the following steps:

S1. smelt: take technically pure iron, chromium, manganese, tin, ferro-silicon is raw material, and adopting lime crucible is 1 * 10 in vacuum tightness ^-4～1 * 10 ^-3in the vacuum induction furnace of Pa, smelt, fusion process adopts refining mode twice, and initial refining temperature is 1550～1600 ℃, and refining time is 30～50min, and secondary refining temperature is 1550～1600 ℃, and refining time is 30～50min;

S2. ingot casting: force deoxidation with fine aluminium, pure magnesium and pure calcium after smelting, carries out ingot casting after vacuum outgas, molten steel casting temperature is 1500～1550 ℃, adopts to control to be cast into steel billet, and pouring pressure is 1～3atm, and pouring speed is 35～40mm/s;

S3. hot rolling: steel billet, after 1250 ℃ of heating coggings are forged, is made steel plate through hot rolling, and hot rolling starting temperature is 1200～1250 ℃, finishing temperature >=850 ℃, air cooling after hot rolling;

S4. pickling and cold-rolling: the steel plate after hot rolling is carried out to pickling, then through draught be greater than 80% cold rolling, make the steel of specified dimension;

S5. recrystallization annealing temperature: cold rollingly rear steel are carried out to recrystallization annealing temperature processing, annealing temperature is 780～800 ℃, and the time is 2～4 hours;

S6. roll: the steel after recrystallization annealing temperature are batched to the steel of making specific thickness 600～650 ℃ of temperature.

Further, carbon content≤0.0218% of described technically pure iron, purity are 99.8～99.9%, purity >=99.5% of chromium, purity >=99.5% of manganese and ferro-silicon, purity >=99.5% of tin.

Further, the pickle solution composition of described pickling is: hydrochloric acid 20%, phosphoric acid 2%, alkyl acid phosphate phenol polyethenoxy ether 1.5%, sodium lauryl tri(oxyethyl) sulfate 1.5%, di-o-tolyl-thiourea 1.5%, pickling additive 2%, pickle solution temperature is controlled at 60～80 ℃.

Composition Design feature of the present invention is: adopt extremely low carbon (≤0.005%), nitrogen (≤0.003%) content, and for remaining C in steel in smelting, N will adopt and add the mode of strong carbonitride microelement Ti and Nb to be fixed, in order to improve ferritic high strength, consider the processing characteristicies such as welding of steel simultaneously, add appropriate reinforced ferrite element: P (0.001～0.010%), Mn (0.10～0.50%) and Si (0.01～0.5%) element, be used for improving the intensity of steel, add appropriate Cr (0.8～1.5%), Mo (0.01～0.1%), Cu (0.05～0.3%) element and be not more than 0.3% Sn element to improving the corrosion resistance of steel, add Mo element can with the acting in conjunction of Sn element, both prevented the red brittleness that Sn element causes in the single segregation of grain boundaries, formed again the common aggregate effect useful to steel highly malleablized, the Ca element and the Sn in steel and the acting in conjunction of S element that add pettiness amount, can further improve the cold-forming property of steel, can also improve the purity of steel, add the Mg element of pettiness amount to carry out degree of depth deoxidation to improve its purity to steel.

Smelting mode of the present invention adopts smelting in induction heating vacuum oven, secondary refining, deep desulfuration deoxidation, vacuum outgas, control casting, in smelting, be particularly further to improve the cleanliness factor of steel, S in steel is reduced to below 0.003%, and the yardstick of nonmetal inclusion is controlled at below 10 μ m.

Adopt Composition Design and process means as above, can obtain of the present invention a kind of containing trace tin element, high strength, the ultra low-carbon steel of corrosion-resistant and easy-formation, can in containing corrosive medium environment, oil and gas field etc. apply, this steel matrix is ferrite, through hot rolling, after cold rolling processing and recrystallization annealing, there is strong { 111} texture, comprise { 111}<110> and { 111}<112> texture, texture degree >35%, its yield strength is 170～260MPa, tensile strength is 350～440MPa, elongation after fracture >=30%, strain-hardening index >=0.15, the coefficient of normal anisortopy >=1.2.

Compare with existing high-strength IF steel, of the present invention have following characteristics containing trace tin element, high strength, ultra low-carbon steel corrosion-resistant and easy-formation:

A. steel of the present invention has lower P content (solution strengthening element P is the highest is no more than 0.1%), and lower Mn, Si content;

B. steel of the present invention contains the Sn element of certain Cr, Cu element and trace simultaneously, to improve the water resistant based sols corrosive power of steel;

C. steel of the present invention is for adopting the Clean Steel with alap S constituent content and nonmetal inclusion content of pure Al, Mg, Ca deoxidation, and this is to guarantee that steel obtain deep drawing quality, the i.e. key of high processability;

D. in steel of the present invention, also contain micro-Mo element, this is because the Mo element that has added a small amount of crystal grain thinning and improved resistance toheat, Mo element can with the acting in conjunction of Sn element, both prevented that Sn element from causing red brittleness in the single segregation of grain boundaries, can form again the common aggregate effect useful to steel highly malleablized.

The present invention has the following advantages:

(1) by adopting, carbon content is no more than 0.0218%, the technically pure iron of purity 99.8%～99.9%, the Sn of the Cr of purity >=99.5%, Mo, Cu, Mn, Si and purity >=99.5% and ferrophosphorus are raw material, the secondary deep deoxidation of secondary refining in vacuum induction furnace and employing Al, Mg, Ca, desulfurization, vacuum outgas, finally obtained the clean high formability energy steel of ultralow C, N content;

(2) for steel of the present invention, after smelting by control cast, cogging forges, after the hot rolling of 850～1250 ℃, carrying out draught, to be greater than 80% multi-pass cold rolling again, after cold rolling, carry out recrystallization annealing processing, annealing temperature is 780～800 ℃, and soaking time is air cooling after 2～4 hours, this makes steel obtain very strong { 111} texture, there is good deep-draw and complicated processability, its strain-hardening index >=0.15, the coefficient of normal anisortopy >=1.2;

(3) adding by P, Mn, Si, Cr solid solution element, strengthened the ferritic performance of steel matrix, by the acting in conjunction with micro alloying element Ti, Nb that adds of Mo element, make steel there is fine crystalline structure, the final steel yield strength obtaining is 170～260MPa, tensile strength is 350～440MPa, elongation after fracture >=30%, have that intensity is high, plasticity good, processability is good feature;

(4) adding by Cr, Cu, Mo, Sn element, improve the corrosion resistance of steel in group water solution, improved the corrosion potential of steel, reduced the corrosion current of steel, improve the pitting corrosion resistant performance of steel, finally obtained the feature of corrosion resistance excellence;

(5) the inventive method principle is reliable, and production technique is simple, easy and simple to handle, practical.

Accompanying drawing explanation

Fig. 1 is embodiment 1 steel after hot rolling and air cooling is processed organizes schematic diagram;

Fig. 2 is that embodiment 1 steel are organized schematic diagram after draught is 80% cold-rolling treatment;

Fig. 3 is embodiment 1 steel after 790 ℃, 3 hours recrystallization annealing temperatures are processed organizes schematic diagram;

Fig. 4 is Mechanics Performance Testing sample and specimen size schematic diagram in embodiment 1-3;

Fig. 5 is the interception way schematic diagram of Mechanics Performance Testing sample in embodiment 1-3.

Embodiment

Below in conjunction with drawings and Examples, the present invention will be further described, and protection scope of the present invention is not limited to the following stated.

Embodiment 1: a kind of ultra low carbon steel slab containing trace tin element, high strength, corrosion-resistant and easy-formation, and described steel plate is composed as follows, is mass percent: C:0.001%, N:0.003%, Mn:0.3%, Cr:0.8%, Mo:0.1, Si:0.2%, Al:0.005%, Mg:0.0015%, Ca:0.0015%, Sn:0.01%, Nb:0.2%, Cu:0.25%, Ti:0.01%, P:0.010%, S:0.003%, all the other are Fe;

The preparation method of above-mentioned ultra low carbon steel slab, it comprises the following steps:

S1. smelt: take carbon content≤0.0218%, purity as 99.8%～99.9% technically pure iron, purity>=99.5% chromium, purity>=99.5% tin, purity>=99.5% manganese, ferro-silicon be raw material, adopting lime crucible is 1 * 10 in vacuum tightness ^-3in the vacuum induction furnace of Pa, smelt, fusion process adopts refining mode twice, and initial refining temperature is 1550 ℃, and refining time is 30min, and secondary refining temperature is 1550 ℃, and refining time is 30min;

S2. ingot casting: force deoxidation with fine aluminium, pure magnesium and pure calcium after smelting, carries out ingot casting after vacuum outgas, molten steel casting temperature is 1500 ℃, adopts to control to be cast into steel billet, adopts to control to be cast into steel billet, and pouring pressure is 1atm, and pouring speed is 35mm/s;

S3. hot rolling: steel billet, after 1250 ℃ of heating coggings are forged, is made steel plate through hot rolling, and hot rolling starting temperature is 1200 ℃, and finishing temperature is 850 ℃, air cooling after hot rolling;

S4. pickling and cold-rolling: the steel plate after hot rolling is carried out to pickling, pickle solution composition is: hydrochloric acid 20%, phosphoric acid 2%, alkyl acid phosphate phenol polyethenoxy ether 1.5%, sodium lauryl tri(oxyethyl) sulfate 1.5%, di-o-tolyl-thiourea 1.5%, pickling additive 2%, pickle solution temperature is controlled at 60 ℃, what through draught, be 80% again is cold rolling, makes the steel plate of specified dimension;

S5. recrystallization annealing temperature: cold rollingly rear steel plate is carried out to recrystallization annealing temperature processing, annealing temperature is 790 ℃, and the time is 3 hours;

S6. roll: the steel plate after recrystallization annealing temperature is batched and makes the steel plate that 8mm is thick 600 ℃ of temperature, after tested, the transformation temperature A of this steel plate _c1be 720～740 ℃, A _c3it is 880～900 ℃.

Above-mentioned steel plate is carried out to mechanics, corrosion resistance electro-chemical test and contextual analysis of organization, and experimental technique and result are as follows:

1. contextual analysis of organization: intercept metallographic specimen on through recrystallization annealing plate, corrode through pre-grinding, polishing and 4% nitric acid alcohol, be prepared into metallographicobservation sample, its microtexture of optical microphotograph Microscopic observation of 500 times.Fig. 1-3 are observations, and wherein Fig. 1 is steel after hot rolling and air cooling is processed, and to organize schematic diagram, Fig. 2 be that steel are organized schematic diagram after draught is 80% cold-rolling treatment, and Fig. 3 is the schematic diagram of organizing after 790 ℃, 3 hours recrystallization annealing temperatures are processed.Metallographicobservation from Fig. 1-3 couple embodiment 1: steel are after hot rolling, for typical single ferritic structure, through after heavy reduction cold rolling, presenting serious ribbon-like fibre shape tissue, the cold rolling ferritic structure by reverting to equiax crystal after recrystallization annealing, its grain fineness number is 9 grades.

2. Mechanics Performance Testing: Mechanics Performance Testing intercepts respectively on the steel plate of recrystallization annealing after cold rolling, the Mechanics Performance Testing of steel adopts plate tensile sample, specimen size as shown in Figure 4, in figure, the unit of specimen size is mm, the following the example of according to parallel with rolling direction, vertical with rolling direction and intercept respectively with rolling direction angular direction at 45 ° of sample.The steel of embodiment 1 is become to 0 °, 45 ° and 90 ° along rolling direction, and line cuts into the tension specimen that gauge length is 50mm, and as shown in Figure 4, the interception way of sample is shown in Fig. 5 to Mechanics Performance Testing sample.

Utilize the true stress-true stain curve of steel unilateral stretching to try to achieve the mean strain hardenability value of steel thick anisotropy index with steel value and Δ r value, the test of r value is to record when draw direction produces 15% strain.

Wherein:

$\stackrel{\&OverBar;}{n}=(n_0+{2n}_{45}+n_{90})/4$

In-plane anisotropy:

It the results are shown in Table 1.

The mechanical experimental results of table 1: embodiment 1 steel

In table: Rel is yield strength, Rm is tensile strength, and A is elongation after fracture, for strain hardening mean value, for the coefficient of normal anisortopy mean value, Δ r is in-plane anisotropy.

3. texture degree is measured:. adopt pit method to measure { the 111} texture of embodiment 1 steel, metallographic pit method is utilized the feature of the low index crystal face preferential etch of isometric system, at the different plate surface of grain orientation, produced different pit, pit has reflected that crystallographic position is to, the texture degree of recrystallization texture from example 1 steel cold rolling with orientation can be directly drawn out in the measurement of pit.

The etching reagent composition that shows the low index crystal face of embodiment 1 steel pit is as follows:

A liquid: H ₂o ₂-15 milliliters, HF-5 milliliter, H ₂o-80 milliliter;

B liquid: HC1-1 milliliter, H ₂o-100 milliliter, FeCl ₃* 6H ₂o-10 gram;

C liquid: 1%HNO ₃spirituous solution.

Pitting nucleation is in A liquid, and B liquid is mainly removed the oxide film on pit surface, and the effect of C liquid is clean surface and shows crystal boundary.

About 200 crystal grain of random observation under the microscope, mark the number of die of favourable orientation, finally calculate the percentage that favourable orientation crystal grain accounts for total number of die, can be similar to the favourable orientation degree that obtains this sample.

Texture degree (favourable orientation degree) %=profit orientation number of die/crystal grain total number X 100%

The calculation result of embodiment 1 steel is: texture degree=38.9%

4. corrosion resistance electro-chemical test: consider the impact of oil and gas engineering down-hole ambient temperature on corrosion, corrosion electrochemistry test is to carry out in the NICE of 50 ℃ of not degasification standardized solution A, adopt three-electrode system: supporting electrode is that platinum electrode, reference electrode are that saturated calomel electrode, Electrode are example 1 sample, solution temperature is with water-bath temperature control at 60 ℃, and electrochemical apparatus is ZF-9 type potentiostat.For the ease of contrast, adopt conventional IF-1 steel as frame of reference.Adopt potentiostatic method measure steel polarization curve, determine the corrosion potential V of steel _corr, corrosion current I _corr; Adopt potentiodynamic scan technique to measure the pitting potential Eb100 of steel.Because embodiment 1 steel and IF-1 steel are Ultra-low carbon low alloy steel, consider that solution is under the condition of not degassing, because the dissolved oxygen in solution is higher, the passivation ability of steel and the stability of passive film strengthen greatly, weaken to a certain extent the sensitivity of pitting potential to pH, thereby can accurately also measure easily the pitting potential of carbon steel/low alloy steel.For this reason, under the condition of not degassing, carry out electrokinetic potential scanning polarimetric test and survey pitting potential.Do not degassing while carrying out polarimetric test, sample is put into after electrolyzer at-1000mV (vs.SCE) cathodic polarization 30min, to remove the oxide film on test face, after current stabilization, control current potential and scan to positive dirction, scanning speed is 1mV/s, and polarizing current is reached to 100 μ A/cm ²potential value is as the critical potential of pitting initiation, i.e. pitting potential Eb100.Test result is in Table 2.

The anticorrosive Electrochemical results of table 2: embodiment 1 steel

As can be seen from Table 2: in embodiment 1 steel, due to the adding of Cr, Mo, Sn element, the corrosion potential of steel is raise compared with IF-1 steel, corrosion current reduces, pitting potential E _b100obviously rise.Compare with conventional I F steel, the more conventional IF steel of corrosion potential of embodiment 1 steel has improved 64mV, and corrosion current value is reduced to 0.0064mA, pitting potential E _b100the 132mV that raise, the corrosion resistance of steel in NICE standardized solution A solution obviously improves.

Embodiment 2: a kind of ultra low carbon steel slab containing trace tin element, high strength, corrosion-resistant and easy-formation, and described steel plate is composed as follows, is mass percent: C:0.005%, N:0.002%, Mn:0.1%, Cr:1.50%, Mo:0.06, Si:0.1%, Al:0.01%, Mg:0.001%, Ca:0.0001%, Sn:0.30%, Nb:0.08%, Cu:0.05%, Ti:0.2%, P:0.005%, S:0.002%, all the other are Fe;

The preparation method of above-mentioned ultra low carbon steel slab, it comprises the following steps:

S1. smelt: take carbon content≤0.0218%, purity as 99.8%～99.9% technically pure iron, purity>=99.5% chromium, purity>=99.5% tin, purity>=99.5% manganese, ferro-silicon be raw material, adopting lime crucible is 1 * 10 in vacuum tightness ^-4in the vacuum induction furnace of Pa, smelt, fusion process adopts refining mode twice, and initial refining temperature is 1600 ℃, and refining time is 50min, and secondary refining temperature is 1600 ℃, and refining time is 50min;

S2. ingot casting: force deoxidation with fine aluminium, pure magnesium and pure calcium after smelting, carries out ingot casting after vacuum outgas, molten steel casting temperature is 1550 ℃, adopts to control to be cast into steel billet, and pouring pressure is 3atm, and pouring speed is 40mm/s;

S3. hot rolling: steel billet, after 1250 ℃ of heating coggings are forged, is made steel plate through hot rolling, and hot rolling starting temperature is 1250 ℃, and finishing temperature is 900 ℃, air cooling after hot rolling;

S4. pickling and cold-rolling: the steel plate after hot rolling is carried out to pickling, pickle solution composition is: hydrochloric acid 20%, phosphoric acid 2%, alkyl acid phosphate phenol polyethenoxy ether 1.5%, sodium lauryl tri(oxyethyl) sulfate 1.5%, di-o-tolyl-thiourea 1.5%, pickling additive 2%, pickle solution temperature is controlled at 80 ℃, what through draught, be 85% again is cold rolling, makes the steel plate of specified dimension;

S5. recrystallization annealing temperature: cold rollingly rear steel plate is carried out to recrystallization annealing temperature processing, annealing temperature is 780 ℃, and the time is 2 hours;

S6. roll: the steel plate after recrystallization annealing temperature is batched and makes the steel plate that 8mm is thick 650 ℃ of temperature.

Above-mentioned steel plate is carried out to mechanics, texture degree mensuration, corrosion resistance electro-chemical test, and experimental technique is with embodiment 1, and texture degree is 39.2%, and mechanical experimental results is as shown in table 4 in table 3, corrosion resistance Electrochemical results:

The mechanical experimental results of table 3: embodiment 2 steel

The anticorrosive Electrochemical results of table 4: embodiment 2 steel

Embodiment 3: a kind of ultra low carbon steel slab containing trace tin element, high strength, corrosion-resistant and easy-formation, and described steel plate is composed as follows, is mass percent: C:0.003%, N:0.001%, Mn:0.5%, Cr:1%, Mo:0.01%, Si:0.5%, Al:0.008%, Mg:0.0001%, Ca:0.0015%, Sn:0.2%, Nb:0.01%, Cu:0.3%, Ti:0.1%, P:0.001%, S:0.001%, all the other are Fe;

The preparation method of above-mentioned ultra low carbon steel slab, it comprises the following steps:

S1. smelt: take carbon content≤0.0218%, purity as 99.8%～99.9% technically pure iron, purity>=99.5% chromium, purity>=99.5% tin, purity>=99.5% manganese, ferro-silicon be raw material, adopting lime crucible is 0.5 * 10 in vacuum tightness ^-4in the vacuum induction furnace of Pa, smelt, fusion process adopts refining mode twice, and initial refining temperature is 1580 ℃, and refining time is 35min, and secondary refining temperature is 1570 ℃, and refining time is 42min;

S2. ingot casting: force deoxidation with fine aluminium, pure magnesium and pure calcium after smelting, carries out ingot casting after vacuum outgas, molten steel casting temperature is 1520 ℃, adopts to control to be cast into steel billet, and pouring pressure is 2atm, and pouring speed is 38mm/s;

S3. hot rolling: steel billet, after 1250 ℃ of heating coggings are forged, is made steel plate through hot rolling, and hot rolling starting temperature is 1230 ℃, and finishing temperature is 950 ℃, air cooling after hot rolling;

S4. pickling and cold-rolling: the steel plate after hot rolling is carried out to pickling, pickle solution composition is: hydrochloric acid 20%, phosphoric acid 2%, alkyl acid phosphate phenol polyethenoxy ether 1.5%, sodium lauryl tri(oxyethyl) sulfate 1.5%, di-o-tolyl-thiourea 1.5%, pickling additive 2%, pickle solution temperature is controlled at 700 ℃, what through draught, be 90% again is cold rolling, makes the steel plate of specified dimension;

S5. recrystallization annealing temperature: cold rollingly rear steel plate is carried out to recrystallization annealing temperature processing, annealing temperature is 800 ℃, and the time is 4 hours;

S6. roll: the steel plate after recrystallization annealing temperature is batched and makes the steel plate that 8mm is thick 625 ℃ of temperature.

Above-mentioned steel plate is carried out to mechanics, texture degree mensuration, corrosion resistance electro-chemical test, and experimental technique is with embodiment 1, and texture degree is 38.5%, and mechanical experimental results is as shown in table 6 in table 5, corrosion resistance Electrochemical results:

The mechanical experimental results of table 5: embodiment 3 steel

The anticorrosive Electrochemical results of table 6: embodiment 3 steel

Claims (5)

1. containing a ultra low-carbon steel for trace tin element, high strength, corrosion-resistant and easy-formation, it is characterized in that, described ultra low-carbon steel is composed as follows, is mass percent:

C:0.001～0.005%, N:0.001～0.003%, Mn:0.1～0.5 %, Cr:0.8～1.50%, Mo:0.01～0.1, Si:0.1～0.5%, Al:0.005～0.01%, Mg:0.0001～0.0015%, Ca:0.0001～0.0015%, Sn:0.01～0.30%, Nb:0.01～0.2%, Cu:0.05～0.3%, Ti:0.01～0.2%, P:0.001～0.010%, S≤0.003%, all the other are Fe.

2. a kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation as claimed in claim 1, it is characterized in that, described steel has { 111} texture by force, texture degree >35%, its yield strength is 170～260MPa, and tensile strength is 350～440MPa, elongation after fracture >=30%, strain-hardening index >=0.15, the coefficient of normal anisortopy >=1.2.

3. the preparation method of a kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation as claimed in claim 1, is characterized in that, it comprises the following steps:

S1. smelt: take technically pure iron, chromium, manganese, tin, ferro-silicon is raw material, and adopting lime crucible is 1 * 10 in vacuum tightness ^-4～1 * 10 ^-3in the vacuum induction furnace of Pa, smelt, fusion process adopts refining mode twice, and initial refining temperature is 1550～1600 ℃, and refining time is 30～50min, and secondary refining temperature is 1550～1600 ℃, and refining time is 30～50min;

S2. ingot casting: force deoxidation with fine aluminium, pure magnesium and pure calcium after smelting, carries out ingot casting after vacuum outgas, molten steel casting temperature is 1500～1550 ℃, adopts to control to be cast into steel billet, and pouring pressure is 1～3atm, and pouring speed is 35～40mm/s;

S3. hot rolling: steel billet, after 1250 ℃ of heating coggings are forged, is made steel plate through hot rolling, and hot rolling starting temperature is 1200～1250 ℃, finishing temperature >=850 ℃, air cooling after hot rolling;

S4. pickling and cold-rolling: the steel plate after hot rolling is carried out to pickling, then through draught be greater than 80% cold rolling, make the steel of specified dimension;

S5. recrystallization annealing temperature: cold rollingly rear steel are carried out to recrystallization annealing temperature processing, annealing temperature is 780～800 ℃, and the time is 2～4 hours;

S6. roll: the steel after recrystallization annealing temperature are batched to the steel of making specific thickness 600～650 ℃ of temperature.

4. the preparation method of a kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation as claimed in claim 3, it is characterized in that, carbon content≤0.0218% of described technically pure iron, purity are 99.8～99.9%, purity >=99.5% of chromium, purity >=99.5% of manganese and ferro-silicon, purity >=99.5% of tin.

5. the preparation method of a kind of ultra low-carbon steel containing trace tin element, high strength, corrosion-resistant and easy-formation as claimed in claim 3, it is characterized in that, the pickle solution composition of described pickling is: hydrochloric acid 20%, phosphoric acid 2%, alkyl acid phosphate phenol polyethenoxy ether 1.5%, sodium lauryl tri(oxyethyl) sulfate 1.5%, di-o-tolyl-thiourea 1.5%, pickling additive 2%, pickle solution temperature is controlled at 60～80 ℃.